1. Technical Field
The present invention relates to an inkjet recording method and recorded matter, and more particularly to an inkjet recording method capable of obtaining recorded matter having uniform glossiness, and recorded matter obtained with that method.
2. Related Art
Inkjet recording methods are printing methods in which printing is performed by making small ink droplets jet and adhere to a recording medium such as paper. Owing to the recent drastic developments in inkjet recording techniques, the inkjet recording methods are now used also for highly precise image recording (printing), which has until now been performed with photography or offset printing. Therefore, high quality recording is required not only for generally used plain paper and dedicated inkjet recoding paper (matte and gloss), but also for recording media such as printing paper.
An ink composition containing water, color material as colorant, water-soluble organic solvent, and surfactant, etc., is generally known as the ink used in the inkjet recording. Dye or pigment is used as the colorant. Particularly in a color ink, water-soluble dyes are often used because of their high color saturation, clarity, and water solubility, etc. However, lightfastness or gas fastness is generally insufficient in those dyes. The waterfastness of those dyes is also insufficient because of their water solubility, and therefore, matter recorded with an ink using water soluble dye has poor recorded image storage stability.
Meanwhile, water-insoluble colorant has better waterfastness. Among water-insoluble colorants, pigment is the color material having particularly excellent lightfastness, gas fastness, and waterfastness. Therefore, pigment inks utilizing those color material properties have been developed. For example, a water-based pigment ink in which pigment is dispersed with surfactant or high polymer dispersant, one using self-dispersing pigment obtained by adding a water dispersible functional group to the pigment surface, and one using coloring particles obtained by covering pigment with water dispersible resin, have been proposed.
Some of those pigment inks have pigment particles (including pigment-containing coloring particles) that are stably dispersed in an ink solution. However, during the process of the ink being dried after being attached to a recording medium such as paper, a structure in the ink changes with evaporation of water or volatile solvent, or because ink solvent is absorbed into an ink absorption layer in a recording medium. Therefore, a stable dispersion structure changes and the pigment is likely to aggregate on the recording medium surface. Accordingly, when recording media such as plain paper and matte paper are used, bright coloration can be obtained because the pigment remains on the recording medium surface. In general, the text quality of a black ink composition obtained on plain paper is often regarded as particularly important, and so the pigment concentration in the ink composition is high. Moreover, an ink composition using a self-dispersing pigment is advantageous in that the coloring ability on plain paper and the pigment concentration in the ink can be increased.
However, when a glossy media is used, concavity and convexity are formed on the media surface because of the pigment remaining on the recording medium, and diffused reflection occurs. For that reason, the glossiness in a portion the ink has been attached to is likely to be lost.
Particularly, when a color image is produced, the pigment amount on a recording medium becomes larger in portions where black ink overlaps with other color ink and the ink concentration becomes high. Compared with a single color image, concavity and convexity are more likely to form in those portions, and therefore, the glossiness is more likely to deteriorate and image uniformity is more likely to be lost (glossiness becoming uneven). Accordingly, the image becomes unnatural, and, as a result, the image quality is lowered.
To solve the above described problems, an inkjet recording method in which, when producing a black image, the amount of yellow and magenta ink used is reduced by using a special color ink such as red ink, and the pigment amount on a recording medium is thereby reduced has been proposed (JP-A-2004-230636).
Also, an ink composition in which uneven glossiness can be reduced with an inkjet ink set and image-recording element combination including: A) an inkjet image-recording element having a gloss value of at least 5 when measured at 60 degrees; B) a pigment based inkjet ink set having at least one pigment-based ink; wherein the normalized differential specular reflectance (NΔRS (x)) for each ink in the set is less than 1.25 when calculated according to a predetermined equation (JP-A-2004-169032).
Also, a recording method in which, when recording composite black by overprinting recording liquids of at least three colors, i.e. yellow, magenta, and cyan, the overprinting sequence of yellow, magenta, and cyan is changed according to the type of recording medium or color tone of the recording liquids, thereby realizing a composite black closer to real black, has been proposed (JP-A-10-166712).
However, in the method using a special color ink such as red ink, the number of ink colors increases and the cost increases accordingly, compared to methods using general YMC inks. The method of reducing uneven glossiness with the inkjet ink set and image-recording element combination lacks versatility. In the method changing the overprinting sequence of yellow, magenta, and cyan, plain paper or coated paper is used as a recording medium. However, the application of that method to a glossy media has not been examined.